Mining Project: Unconventional Monitoring and Design for Mine Stability in Sedimentary Rock

Research Summary

Despite significant advancements in mine safety technology and practices in the past 20 years, accidents that result in permanent disabilities and fatalities continue to occur in underground mines. U.S. underground coal mines reported 25,171 accidents related to ground control between 2000 and 2019. Of these, 158 involved fatalities or resulted in permanent or total disability. Significant contributing factors include the highly variable nature of the host rock, an incomplete understanding of how localized changes in rock properties impact ground stability, and a lack of affordable ground stability monitoring technologies appropriate to an underground setting. Operators need non-invasive, low-cost, and user-friendly ground monitoring technologies to understand and anticipate failures prior to their occurrence, which would ultimately result in the reduction of injury-accidents associated with failures of ground.

A significant concern often expressed by industry is the complexity of sensors and data analysis used for ground stability monitoring. Robust, inexpensive instruments that provide clear, actionable information are necessary to facilitate routine use by operators. Currently available technology does not meet this industry need, and advancement of mining-induced seismic monitoring has been identified by NIOSH mine collaborators and by the 2019 Mining Program review as a candidate technology to address this need. The overarching goal is to widen the application of seismic monitoring and other remote sensing techniques to include softrock settings, where widespread industry adoption has yet to be realized. Specifically, this project seeks to ameliorate those obstacles that prevent widespread industry adoption, including high costs, lack of validation in diverse softrock settings, difficulty of use or the need for specialized skills for data interpretation, and raising industry awareness of available monitoring tools.

To address these issues, this project will undertake three research aims, as described below.

1. Provide mine operators with an arsenal of low-cost, non-invasive geophysical ground assessment methods. The approach will merge instrumentation data, modeling, and observed seismicity in sedimentary environments. The central goal is to determine how mining operations can be conducted more safely through the adoption of ground monitoring methods. If the results of data integration indicate no significant risk to mine stability and safety, there is validation of the current design and operation. If the safety factors are low and result in an unsafe, unstable situation, changes can be made on the basis of these data to modify operations that will result in safer ground conditions.
2. Evaluate geochemical markers for their potential as early indicators for risk of gas-driven dynamic failure events. This research aim seeks to explore the gas-generating potential of coal through geochemical and geologic analysis of coal and coal measure strata. These data will be used to develop an early risk assessment index for violent rib failure in which internal gas pressure is a contributing risk factor. By identifying areas of high risk early—ideally during the exploration phase of mining—mines may be designed to account for these states of heightened risk, thereby facilitating the proactive avoidance of dangerous conditions prior to worker exposure.
3. Provide mine operators with a practical approach for seismic monitoring at sedimentary underground mines. There are three categories of challenges that need to be addressed before softrock mines will fully realize the safety benefits of seismic monitoring: monitoring technology (hardware), data processing (software), and awareness and interpretation (education). The purpose of this research aim is to address these challenges, particularly the latter two, as advances in instrumentation made by other entities are beginning to address the first issue.

The projected impacts of the proposed research are twofold. First, completion of the research will provide mine operators with proven, affordable tools for ground condition monitoring, which can alert operators to hazardous areas prior to worker injury. Second, validation of proposed methodologies, inclusive of seismic monitoring and geochemical analyses, will facilitate an improvement in the understanding of ground condition changes over time, which may then lead to the more effective use of proactive design and support practices. These impacts will yield the outcome of achieving a further reduction in the overall number of ground-fall-related accidents in underground coal mines, and also, but perhaps more importantly, result in the reduction of injury rates through improved early hazard detection.